The Transportation Security Administration (TSA) is trying to ensure that servicemembers and Department of Defense (DoD) civilians know they can use the TSA Precheck program. All servicemembers and students at the armed forces' service academies are automatically enrolled in TSA Precheck. Their DoD ID number (a 10-digit number that should be on the back of their Common Access Card) serves as their Known Traveler Number. For more details, see this Military.com article.